Airsmart Technology R801W-3DI, Руководство пользователя

Страница: 20 / 23

○
9
⑩
How to test the effect of an
external antenna?
Must the external antenna be very high and long?
In a general listening environment,
turn the radio to a relatively weak
shortwave radio station, and go outside
of the room while listening. If the
shortwave radio signal is enhanced,
outdoor antenna should be installed to
improve the receiving effect. However,
if there is a strong TV station, FM
radio, BP machine and other radio
communication antenna near the
receiving location, the strong
interference signal will cause poor
receiving effect of shortwave external
antenna.
In short, shortwave external antenna will get better effect if it is high and long. But, higher and longer antenna doesn’t
imply better effect. Sometimes, sensitive antenna will introduce strong radio interference wave. Therefore, the height
and length of the external antenna should be adjusted according to the actual needs.
○
11
FM broadcasting
FM (FM) is a close-range high-fidelity radio system, which is the broadcast system with most rapid development, the
largest number, and best sound quality.
In some developed countries, a city even has 30 FM radio stations. Since the 1980s, China has built a large number of
FM radio stations, and almost all of them can play stereo programs. China FM radio frequency: 87 ~ 108 MHz, the
frequency interval 0.1 MHz, radio frequency from several hundred watts to twenty kilowatts.
Special warning: do
not install outdoor
antenna in the
multi-lightning area!
○
12
What signal will affect FM reception?
Powerful VHF TV radio broadcasting and personal
computer switching power supply radio wave will
interfere with the FM reception. In addition, the
FM radio stations with adjacent frequency and
strong transmitting power will interfere with each
other, leading to poor reception effect.
○
13
How far is the receiving distance of
the FM radio?
FM radio frequency is very high, and the radio is
transmitted in a linear way. The higher the
transmitting antenna, the greater the power, the
larger the coverage, and the farther the transmission
distance. FM radio transmission distance is usually
30 to 100 km.